I fully agree with Don.
ebay has had a major impact on the stamp hobby..
Before the year 2000, many stamps I collected like Thailand revenues were extremely rare and nearly impossible to find for any price!
After the year 2000 when
ebay became more popular it was suddenly possible to buy for quite low prices single stamps missing from sets or other lower value stamps. No auction house sells 1 dollar stamps in auction, that means you had to buy box lots or larger country collections, resulting in huge amounts of excess stamps.
Lots of long dormant material could find its way into the market via
ebay.
Yes,
ebay makes a lot of irritating changes like the global shipping program (irritating at least for me living in Thailand and being asked to pay $47 shipping on a $1 value stamp). But like every new rules in the world, we can try to live with it or find ways o mitigate the impact.
As a seller of stamps,
ebay is the only auction site with enough bidders to make it possible to list auction style lots all starting at $.99 and still get good final selling results.
Hipstamps and Delcampe are only suitable for fixed price auctions due to lower amount of bidders.
So all in all,
ebay is a great contributor for our hobby.